Keep in mind that most fruits when grown from seed will not produce the same fruit as the tree that it came from. Some will never produce fruit. Do not use any fertilizers until the tree is at least a foot tall. Using fertilizers at this point will kill the seedlings. They have enough food storage in the seed shell to last up to a few months. I would just use a good potting soil until they are about a year old. Then you can transplant them out.